Light filter and spectrometer including the same

ABSTRACT

A light filter and a spectrometer including the light filter are disclosed. The light filter includes a plurality of filter units having different resonance wavelengths, wherein each of the plurality of filter units includes a cavity layer configured to output light of constructive interference, a Bragg reflection layer provided on a first surface of the cavity layer, and a pattern reflection layer provided on a second surface of the cavity layer opposite to the first surface and configured to cause guided mode resonance of light incident on the pattern reflection layer, the pattern reflection layer including a plurality of reflection structures that are periodically arranged.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application Nos.10-2018-0028293 and 10-2018-0133136, filed on Mar. 9, 2018 and Nov. 1,2018, respectively, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in their entirety byreference.

BACKGROUND 1. Field

Example embodiments of the present disclosure relate to a light filterand a spectrometer including the light filter.

2. Description of the Related Art

A spectrometer is an optical tool. Spectrometers of the related artinclude various optical elements, and thus are relatively bulky andheavy. In recent years, smaller spectrometers have been needed for insmall-device applications such as smartphones or wearable devices. Inparticular, spectrometers having an on-chip structure may be smallerbecause integrated circuits and optical devices are all formed on onesemiconductor chip, and thus on-chip spectrometers have been developed.

SUMMARY

One or more example embodiment provide light filters and spectrometersincluding the light filters.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of example embodiments.

According to an aspect of an example embodiment, there is provided alight filter including a plurality of filter units having differentresonance wavelengths, wherein each of the plurality of filter unitsincludes a cavity layer configured to output light of constructiveinterference, a Bragg reflection layer provided on a first surface ofthe cavity layer, and a pattern reflection layer provided on a secondsurface of the cavity layer opposite to the first surface and configuredto cause guided mode resonance of light incident on the patternreflection layer, the pattern reflection layer including a plurality ofreflection structures that are periodically provided.

The plurality of reflection structures may be periodically provided witha pitch less than a resonance wavelength of each of the plurality offilter units.

The resonance wavelength of each of the plurality of filter units may bedetermined by at least one of a pitch, a thickness, and a duty cycle ofthe plurality of reflection structures.

The plurality of reflection structures may be providedone-dimensionally.

The plurality of reflection structures may be provided as parallellines.

The plurality of reflection structures may be providedtwo-dimensionally.

The plurality of reflection structures may be repeatedly provided in apolygonal pattern.

The Bragg reflection layer may include a plurality of material layersrespectively having different refractive indexes that are alternatelystacked.

The pattern reflection layer may further include a filling layer filledin gaps between the plurality of reflection structures, and a refractiveindex of the filling layer may be different from a refractive index ofthe plurality of reflection structures.

The pattern reflection layer may further include a cover layer coveringthe plurality of reflection structures, and a refractive index of thecover layer may be different from a refractive index of the plurality ofreflection structures.

According to an aspect of another example embodiment, there is provideda light filter including a plurality of filter units having differentresonance wavelengths, wherein each of the plurality of filter unitsinclude a cavity layer configured to output light of constructiveinterference, a first Bragg reflection layer provided on a first surfaceof the cavity layer, a second Bragg reflection layer provided on asecond surface of the cavity layer opposite to the first surface, and apattern reflection layer provided in the cavity layer and configured tocause guided mode resonance of light incident on the pattern reflectionlayer, the pattern reflection layer including a plurality of reflectionstructures that are periodically provided.

The plurality of reflection structures may be periodically provided witha pitch less than a resonance wavelength of each of the plurality offilter units.

The resonance wavelength of each the plurality of filter units may bedetermined by at least one of a pitch, a thickness, and a duty cycle ofthe plurality of reflection structures.

The plurality of reflection structures may be provided one-dimensionallyor two-dimensionally.

Each of the first Bragg reflection layer and the second Bragg reflectionlayer may respectively include a plurality of material layers havingdifferent refractive indexes that are alternately stacked.

The plurality of reflection structures may be provided on a surface ofthe first Bragg layer adjacent to the first surface of the cavity layeror a surface of the second Bragg layer adjacent to the second surface ofthe cavity layer.

The plurality of reflection structures may be in contact with the firstBragg layer and the second Bragg layer.

According to an aspect of an example embodiment, there is provided aspectrometer including a light filter including a plurality of filterunits, the plurality of filter units having different resonancewavelengths, and a sensing unit configured to receive light that haspassed through the light filter, wherein each of the plurality of filterunits includes a cavity layer configured to output light of constructiveinterference, a first Bragg reflection layer provided on a first surfaceof the cavity layer, and a pattern reflection layer including aplurality of reflection structures that are provided on a second surfaceof the cavity layer opposite to the first surface or included in thecavity layer, the pattern reflection layer being configured to causeguided mode resonance of light incident on the pattern reflection layer.

The plurality of reflection structures may be periodically provided witha pitch less than a resonance wavelength of each of the plurality offilter units.

The resonance wavelength of each of the plurality of filter unit may bedetermined by at least one of a pitch, a thickness, and a duty cycle ofthe plurality of reflection structures.

The plurality of reflection structures may be provided one-dimensionallyor two-dimensionally.

The plurality of reflection structures may be provided on the secondsurface of the cavity layer, wherein the pattern reflection layer mayfurther include a filling layer filled in gaps between the plurality ofreflection structures, and a refractive index of the filling layer maybe different from a refractive index of the plurality of reflectionstructures.

The plurality of reflection structures may be provided in the cavitylayer, and each of the plurality of filter units may further include asecond Bragg layer provided on the second surface of the cavity layer.

The sensing unit may include an image sensor or a photodiode.

The pattern reflection layer may further include a plurality ofconnection layers configured to connect adjacent reflection structures,and a thickness of the connection layer may be less than a thickness ofthe plurality of reflection structures.

The plurality of reflection structures may be in contact with the firstBragg layer and the second Bragg layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view schematically illustrating a spectrometeraccording to an example embodiment;

FIG. 2 is a perspective view illustrating a filter unit of a lightfilter shown in FIG. 1;

FIG. 3 is a cross-sectional view illustrating the filter unit shown inFIG. 2;

FIG. 4 is a view illustrating a filter unit of the related art as anexample model;

FIG. 5 is a view illustrating simulation results of transmission spectraof the filter unit shown in FIG. 4;

FIG. 6 is a view illustrating an example model of the filter unit of theembodiment shown in FIG. 2;

FIGS. 7A, 7B, and 7C are views illustrating simulation results oftransmission spectra of the filter unit shown in FIG. 6;

FIG. 8 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 9 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 10 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 11 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 12 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 13 is a view illustrating a filter unit according to an exampleembodiment;

FIGS. 14A and 14B are views illustrating a filter unit according to anexample embodiment;

FIG. 15 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 16 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 17 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 18 is a view illustrating a filter unit according to an exampleembodiment;

FIG. 19 is a view illustrating a filter unit according to an exampleembodiment;

FIGS. 20A and 20B are views illustrating a filter unit according to anexample embodiment;

FIGS. 21A and 21B are views illustrating a filter unit according to anexample embodiment;

FIGS. 22A and 22B are views illustrating a filter unit according to anexample embodiment;

FIGS. 23A and 23B are views illustrating a filter unit according to anexample embodiment;

FIGS. 24A and 24B are views illustrating a filter unit according to anexample embodiment;

FIGS. 25A and 25B are views illustrating a filter unit according to anexample embodiment; and

FIGS. 26A and 26B are views illustrating a filter unit according to anexample embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments, examples ofwhich are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout, and the sizes ofelements may be exaggerated for clarity of illustration. In this regard,the present embodiments may have different forms and should not beconstrued as being limited to the descriptions set forth herein.Accordingly, example embodiments are merely described below, byreferring to the figures, to explain aspects.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list. Forexample, the expression, “at least one of a, b, and c,” should beunderstood as including only a, only b, only c, both a and b, both a andc, both b and c, or all of a, b, and c.

In the following description, when an element is referred to as being“above” or “on” another element, it may be directly on the other elementwhile making contact with the other element or may be above the otherelement without making contact with the other element. The terms of asingular form may include plural forms unless specifically mentioned. Itwill be further understood that the terms “comprises” and/or“comprising” used herein specify the presence of stated features orelements, but do not preclude the presence or addition of one or moreother features or elements.

An element referred to with the definite article or a demonstrativepronoun may be construed as the element or the elements even though ithas a singular form. Operations of a method may be performed inappropriate order unless explicitly described in terms of order ordescribed to the contrary. That is, operations are not limited to theorder in which the operations are described. In the present disclosure,examples or exemplary terms (for example, “such as” and “etc.”) are usedfor the purpose of description and are not intended to limit the scopeof the inventive concept unless defined by the claims.

FIG. 1 is a perspective view illustrating schematically illustrating aspectrometer 3000 according to an example embodiment.

Referring to FIG. 1, the spectrometer 3000 includes a sensing device3200 and a light filter 3100 provided on the sensing device 3200. Thelight filter 3100 may include a plurality of filter units 100 arrangedin a two-dimensional array pattern. However, example embodiment are notlimited thereto. For example, the filter units 100 may be arranged in aone-dimensional array pattern. The filter units 100 may have differentresonance wavelengths. However, the filter units 100 are not limitedthereto. For example, some of the filter units 100 may have the sameresonance wavelength.

The sensing device 3200 may receive light having passed through thelight filter 3100 and may convert the light into an electrical signal.After light incident on the light filter 3100 passes through the filterunits 100, the light have different resonance wavelengths and reachespixels of the sensing device 3200. Then, the sensing device 3200converts the light incident on the pixels into an electrical signal. Forexample, the sensing device 3200 may include a photodiode or an imagesensor such as a charge coupled device (CCD) image sensor or acomplementary metal-oxide semiconductor (CMOS) image sensor.

FIG. 2 is a perspective view illustrating a filter unit 100 of the lightfilter 3100 shown in FIG. 1, and FIG. 3 is a cross-sectional viewillustrating the filter unit 100 shown in FIG. 2.

Referring to FIGS. 2 and 3, the filter unit 100 may include a cavitylayer 110, a Bragg reflection layer 120 provided on a surface of thecavity layer 110, and a pattern reflection layer 130 provided on anopposite surface of the cavity layer 110.

The Bragg reflection layer 120 may be provided on a surface of thecavity layer 110, for example, a lower surface of the cavity layer 110.The Bragg reflection layer 120 may be a distributed Bragg reflector(DBR). The Bragg reflection layer 120 may have a structure in which aplurality of material layers having different refractive indexes arealternately stacked. The Bragg reflection layer 120 having such astructure may reflect light by periodic variations in refractive index.

FIG. 3 illustrates an example in which the Bragg reflection layer 120includes first material layer 121 and second material layer 122 thathave different refractive indexes and are each alternately stacked threetimes. The first and second material layers 121 and 122 may includesemiconductor materials having different refractive indexes. Forexample, the first material layer 121 may include silicon dioxide (SiO₂)(refractive index=about 1.46), and the second material layer 122 mayinclude silicon (Si) (refractive index=about 3.8). However, this ismerely an example. For example, the first and second material layers 121and 122 may include various other materials depending on designconditions such as the wavelength of incident light.

The pattern reflection layer 130 may be provided on an opposite surfaceof the cavity layer 110, for example, an upper surface of the cavitylayer 110. Here, the pattern reflection layer 130 may increasereflectance in a narrow wavelength range by causing guide mode resonance(GMR). To this end, the pattern reflection layer 130 may have a gratingstructure configured to cause GMR. The pattern reflection layer 130 mayinclude a plurality of reflection structures 135 that are periodicallyarranged at regular intervals on the upper surface of the cavity layer110. In this example, the reflection structures 135 may be arranged witha pitch P less than a resonance wavelength corresponding to the filterunit 100.

In the example embodiment, the reflection structures 135 of the patternreflection layer 130 may be arranged on the upper surface of the cavitylayer 110 in a one-dimensional pattern. For example, each of thereflection structures 135 may have a line shape having a width (w) and athickness (t), and the reflection structures 135 may be arranged in onedirection with a pitch (P) and may be parallel to each other. FIG. 3illustrates an example in which each of the reflection structures 135has a tetragonal cross-sectional shape. However, this is merely anexample. For example, each of the reflection structures 135 may haveother polygonal cross-sectional shape such as a triangularcross-sectional shape.

The reflection structures 135 may include a semiconductor materialhaving a given refractive index. For example, the reflection structures135 may include Si (refractive index=about 3.8). However, this is anon-limiting example. For example, the reflection structures 135 mayinclude a material such as gallium arsenide (GaAs), gallium phosphide(GaP), silicon nitride (SiN) or titanium dioxide (TiO₂). In addition,the reflection structures 135 may include various materials depending ondesign conditions such as the wavelength of incident light.

In the example embodiment, the resonance wavelengths of each of thefilter units 100 of the light filter 3100 may be determined by at leastone of the pitch (P), thickness (t), and duty cycle of the reflectionstructures 135. Therefore, the filter units 100 having differentresonance wavelengths may be more easily implemented by varying at leastone of the pitch (P), thickness (t), and duty cycle of the reflectionstructures 135 of the pattern reflection layers 130.

The cavity layer 110 may be provided between the Bragg reflection layer120 and the pattern reflection layer 130. The cavity layer 110 mayinclude a material having a refractive index less than the reflectionstructures 135 of the pattern reflection layer 130. For example, thecavity layer 110 may include SiO₂ (refractive index=about 1.46).However, this is merely an example. For example, the cavity layer 110may include various materials depending on design conditions such as thewavelength of incident light.

In this structure, light IL entering the cavity layer 110 from an uppersurface of the filter unit 100 may travel in the cavity layer 110between the Bragg reflection layer 120 and the pattern reflection layer130 while experiencing constructive interference and destructiveinterference. Then, light TL having a resonance wavelength satisfyingconstructive interference conditions of the cavity layer 110 may exitthe filter unit 100 through a lower surface of the filter unit 100. Thatis, the cavity layer 110 is configured to output light of a givenresonance wavelength.

According to the example embodiment, since the filter unit 100 includesthe pattern reflection layer 130 having a grating structure capable ofcausing GMR, reflectance may be increased in a narrow wavelength range.Therefore, variations in resonance wavelength caused by variations inthe incident angle of light IL on the filter unit 100 may be reduced. Inaddition, the filter units 100 having different resonance wavelengthsmay be more easily implemented by varying the pitch (P), thickness (t),or duty cycle of the reflection structures 135 of the pattern reflectionlayers 130. Therefore, the light filter 3100 may be fabricated through asimpler process at lower costs and in a shorter period of time.

FIG. 4 is a view illustrating a filter unit 10 of the related art as anexample model.

In the filter unit 10 of the related art shown in FIG. 4, a first Braggreflection layer 12 and a second Bragg reflection layer 13 arerespectively provided on a lower surface and an upper surface of acavity layer 11. In the example, the first and second Bragg reflectionlayers 12 and 13 include SiO₂ layers (thickness=about 145 nm, refractiveindex=about 1.46) as first material layers 12′ and 13′, and Si layers(thickness=about 56 nm, refractive index=about 3.8) as second materiallayers 12″ and 13″. In each of the first and second Bragg reflectionlayers 12 and 13, the SiO₂ layers and the Si layers are each alternatelystacked three times, and the cavity layer 11 includes an SiO₂ layer(thickness=about 290 nm, refractive index=about 1.46).

In this structure, light IL1 incident on the cavity layer 11 travels inthe cavity layer 11 while being reflected between the first and secondBragg reflection layers 12 and 13. Then, light TL1 having a givenresonance wavelength is output to the outside through the first Braggreflection layer 12.

FIG. 5 is a view illustrating simulation results of transmission spectraof the filter unit 10 shown in FIG. 4. FIG. 5 illustrates transmissionspectra calculated while sequentially varying the incident angle θ oflight IL1 on the filter unit 10 from 0° to 10°.

Referring to FIG. 5, in the filter unit 10 of the related art in whichthe first and second Bragg reflection layers 12 and 13 are respectivelyprovided on the lower and upper surfaces of the cavity layer 11, theresonance wavelength was significantly varied with variations in theincident angle of light IL1. When the resonance wavelength significantlyvaries with variations in the incident angle of light IL1, the fullwidth at half maximum (FWHM) in transmission spectrum may increase, andthus the resolution of a spectrometer may deteriorate.

FIG. 6 is a view illustrating an example model 200 of the filter unit100 of the example embodiment shown in FIG. 2. Referring to FIG. 6, aBragg reflection layer 220 includes SiO₂ layers (thickness=about 145 nm,refractive index=about 1.46) as first material layers 221 and Si layers(thickness=about 56 nm, refractive index=about 3.8) as second materiallayers 222. The SiO₂ layers and the Si layers are each alternatelystacked three times, and a cavity layer 210 includes an SiO₂ layer(thickness=about 290 nm, refractive index=about 1.46). In addition, eachof reflection structures 235 may include Si with a filling ratio ofabout 0.5 (thickness=about 200 nm, refractive index=about 3.8), andother configurations of the filter unit 200 may be the same as thefilter unit 100 shown in FIG. 3.

FIGS. 7A to 7C are views illustrating simulation results of transmissionspectra of the filter unit 200 shown in FIG. 6.

FIG. 7A illustrates transmission spectra calculated while varying theincident angle θ of light IL2 on the filter unit 200 from 0° to 2°, 4°,6°, 8°, and 10° under the condition that the reflection structures 235of the filter unit 200 have a pitch (P) of 280 nm.

Referring to FIG. 7A, when the incident angle θ of light IL2 was 0°, theresonance wavelength was 782.68 nm, and when the incident angle θ oflight IL2 was varied from 0° to 10°, the resonance wavelength was variedby about 0.89 nm. In addition, light TL2 having passed through thefilter unit 200 had a maximum intensity of about 0.872 and an FWHM ofabout 3.19 nm.

FIG. 7B illustrates transmission spectra calculated while varying theincident angle θ of light IL2 on the filter unit 200 from 0° to 2°, 4°,6°, 8°, and 10° under the condition that the reflection structures 235of the filter unit 200 have a pitch (P) of 320 nm.

Referring to FIG. 7B, when the incident angle θ of light IL2 was 0°, theresonance wavelength was 813.47 nm, and when the incident angle θ oflight IL2 was varied from 0° to 10°, the resonance wavelength was variedby about 0.97 nm. In addition, light TL2 having passed through thefilter unit 200 had a maximum intensity of about 0.968 and an FWHM ofabout 1.41 nm.

FIG. 7C illustrates transmission spectra calculated while varying theincident angle θ of light IL2 on the filter unit 200 from 0° to 2°, 4°,6°, 8°, and 10° under the condition that the reflection structures 235of the filter unit 200 have a pitch (P) of 340 nm.

Referring to FIG. 7C, when the incident angle θ of light IL2 was 0°, theresonance wavelength was 825.88 nm, and when the incident angle θ oflight IL2 was varied from 0° to 10°, the resonance wavelength was variedby about 1.0 nm. In addition, light TL2 having passed through the filterunit 200 had a maximum intensity of about 0.72 and an FWHM of about 3.8nm.

Referring to the results shown in FIGS. 7A to 7C, it could be understoodthat the resonance wavelength varies less although the incident angle θof light IL2 on the filter unit 200 shown in FIG. 6 is varied, and ahigher resolution is obtained due to a smaller FWHM.

FIG. 8 is a view illustrating a filter unit 300 according to an exampleembodiment.

Referring to FIG. 8, the filter unit 300 includes a cavity layer 110, aBragg reflection layer 120 provided on a surface of the cavity layer110, and a pattern reflection layer 330 provided on an opposite surfaceof the cavity layer 110. The Bragg reflection layer 120 may have astructure in which a plurality of material layers having differentrefractive indexes are alternately stacked. FIG. 8 illustrates anexample in which the Bragg reflection layer 120 includes first andsecond material layers 121 and 122 that have different refractiveindexes and are each alternately stacked three times.

The pattern reflection layer 330 may increase reflectance in a narrowwavelength range by causing GMR. To this end, the pattern reflectionlayer 330 may have a grating structure configured to cause GMR. Thepattern reflection layer 330 may include a plurality of reflectionstructures 335 periodically arranged at given intervals, and a fillinglayer 345 filled in gaps between the reflection structures 335. Thereflection structures 335 may be arranged on an upper surface of thecavity layer 110 in a one-dimensional pattern. Each of the reflectionstructures 335 may have a line shape having a width and a thickness, andthe reflection structures 335 may be arranged in one direction with agiven pitch in parallel to each other.

The reflection structures 335 may be arranged with a pitch less than aresonance wavelength corresponding to the filter unit 300. Each of thereflection structures 335 may have a polygonal cross-sectional shapesuch as a tetragonal or triangular cross-sectional shape and may includea semiconductor material having a given refractive index. However,example embodiments are not limited thereto. The reflection structures335 may include various materials depending on design conditions such asthe wavelength of incident light.

The filling layer 345 may be provided on the upper surface of the cavitylayer 110 to fill gaps between the reflection structures 335. Thefilling layer 345 may have the same thickness as the reflectionstructures 335. However, the filling layer 345 is not limited thereto.For example, the filling layer 345 may be thinner than the reflectionstructures 335. The filling layer 345 may include a material having arefractive index different from the refractive index of the reflectionstructures 335.

The filling layer 345 may include a material having a refractive indexless than the refractive index of the reflection structures 335. Forexample, the reflection structures 335 may include a relatively highreflective index material such as Si, GaAs, GaP, SiN, or TiO₂, and thefilling layer 345 may include a material such as SiO₂, a polymer-basedmaterial (SU-8, PMMA), or hydrogen silsesquioxane (HSQ) having arefractive index less than the refractive index of the reflectionstructures 335. However, this is merely an example. The reflectionstructures 335 and the filling layer 345 may include various materialsother than the above-listed materials.

In the above, it is described that the reflection structures 335 includea material having a refractive index greater than the refractive indexof the filling layer 345. However, this is a non-limiting example. Forexample, the reflection structures 335 may include a material having arefractive index less than the refractive index of the filling layer345.

According to the example embodiment, since the filter unit 300 includesthe pattern reflection layer 330 having a grating structure capable ofcausing GMR, reflectance may be increased in a narrow wavelength range,and thus variations in resonance wavelength caused by variations in theincident angle of light on the filter unit 300 may be reduced. Inaddition, since the resonance wavelength of the filter unit 300 may bedetermined by varying the pitch, thickness, or duty cycle of thereflection structures 335 of the pattern reflection layer 330, a lightfilter including filter units 300 having different resonance wavelengthsmay be more easily fabricated.

FIG. 9 is a view illustrating a filter unit 400 according to an exampleembodiment.

Referring to FIG. 9, the filter unit 400 includes a cavity layer 110, aBragg reflection layer 120 provided on a surface of the cavity layer110, and a pattern reflection layer 430 provided on an opposite surfaceof the cavity layer 110. The pattern reflection layer 430 may have agrating structure configured to cause GMR. The pattern reflection layer430 may include a plurality of reflection structures 435 periodicallyarranged at given intervals, and a cover layer 450 covering thereflection structures 435.

The cover layer 450 may be provided on an upper surface of the cavitylayer 110 to cover and encapsulate the reflection structures 435. Thecover layer 450 may include a material having a refractive indexdifferent from the refractive index of the reflection structures 435.For example, the cover layer 450 may include a material having arefractive index less than the refractive index of the reflectionstructures 435. However, this is a non-limiting example. For example,the reflection structures 435 may include a material having a refractiveindex less than the refractive index of the cover layer.

The other structures shown in FIG. 9 are described in the previousexample embodiments, and thus descriptions thereof will not be repeatedhere.

FIG. 10 is a view illustrating a filter unit 500 according to an exampleembodiment.

Referring to FIG. 10, the filter unit 500 includes a cavity layer 110, aBragg reflection layer 120 provided on a surface of the cavity layer110, and a pattern reflection layer 530 provided on an opposite surfaceof the cavity layer 110. The pattern reflection layer 530 may have agrating structure capable of causing GMR. The pattern reflection layer530 may include a plurality of reflection structures 535 periodicallyarranged at given intervals, and a connection layer 560 connecting thereflection structures 535.

The connection layer 560 may be provided on an upper surface of thecavity layer 110 to connect the adjacent reflection structures 535. Theconnection layer 560 may have a thickness that is less than thethickness of the reflection structures 535. The connection layer 560 maybe provided in one piece with the reflection structures 535 and mayinclude the same material that the reflection structures 535 include.

The other structures shown in FIG. 10 are described in the previousexample embodiments, and thus descriptions thereof will not be repeatedhere.

FIG. 11 is a view illustrating a filter unit 600 according to an exampleembodiment.

Referring to FIG. 11, the filter unit 600 includes a cavity layer 610, afirst Bragg reflection layer 620 provided on a surface of the cavitylayer 610, a second Bragg reflection layer 640 provided on an oppositesurface of the cavity layer 610, and a pattern reflection layer 630provided in the cavity layer 610.

The first and second Bragg reflection layers 620 and 640 mayrespectively be provided on a lower surface and an upper surface of thecavity layer 610. Each of the first and second Bragg reflection layers620 and 640 may have a structure in which a plurality of material layershaving different refractive indexes are alternately stacked. In theexample shown in FIG. 11, the first Bragg reflection layer 620 includesfirst material layer 621 and second material layer 622 having differentrefractive indexes, and the second Bragg reflection layer 640 includesfirst material layer 641 and second material layer 642 having differentrefractive indexes. In this case, the first material layers 621 and 641and the second material layers 622 and 642 may include various materialsdepending on design conditions such as the wavelength of incident light.The first and second Bragg reflection layers 620 and 640 having such astructure may reflect light by periodic variations in refractive index.

The cavity layer 610 is provided between the first and second Braggreflection layers 620 and 640, and the pattern reflection layer 630 maybe provided in the cavity layer 610. Here, the pattern reflection layer630 may be provided on an inner surface (that is, an upper surface) ofthe first Bragg reflection layer 620.

The pattern reflection layer 630 may cause GMR and may include aplurality of reflection structures 635 provided in the cavity layer 610and periodically arranged at regular intervals on the upper surface ofthe first Bragg reflection layer 620. Here, the reflection structures635 may be arranged with a pitch less than a resonance wavelengthcorresponding to the filter unit 600.

The reflection structures 635 of the pattern reflection layer 630 may bearranged in a one-dimensional pattern similar to the reflectionstructures 135 shown in FIG. 2. For example, each of the reflectionstructures 635 may have a line shape having a width and a thickness, andthe reflection structures 635 may be arranged in one direction with agiven pitch in parallel to each other. In addition, although thereflection structures 635 shown in FIG. 11 have a tetragonalcross-sectional shape, this is a non-limiting example. For example, eachof the reflection structures 635 may have any other polygonalcross-sectional shape.

The reflection structures 635 may include a semiconductor materialhaving a given refractive index. For example, the reflection structures635 may include a material having a refractive index greater than therefractive index of the cavity layer 610. The reflection structures 635may include various materials depending on design conditions such as thewavelength of incident light.

In this structure of the filter unit 600, light entering the cavitylayer 610 through the second Bragg reflection layer 640 may travelbetween the second Bragg reflection layer 640 and the pattern reflectionlayer 630, and after travelling in the cavity layer 610, light having agiven resonance wavelength may be output to the outside through thepattern reflection layer 630 and the first Bragg reflection layer 620.

According to the example embodiment, since the pattern reflection layer630 causing GMR is provided in the cavity layer 610 of the filter unit600, reflectance may be increased in a narrow wavelength range.Therefore, variations in resonance wavelength caused by variations inthe incident angle of light on the filter unit 600 may be reduced. Inaddition, filter units 600 having different resonance wavelengths may beimplemented by varying the pitch, thickness, or duty cycle of thereflection structures 635 of the pattern reflection layer 630, and thusit may be possible to simplify manufacturing processes of a light filterand reduce manufacturing costs and time.

FIG. 12 is a view illustrating a filter unit 700 according to an exampleembodiment. The filter unit 700 shown in FIG. 12 is the same as thefilter unit 600 shown in FIG. 11 except that a pattern reflection layer730 is provided on an inner surface of a second Bragg reflection layer640.

FIG. 13 is a view illustrating a filter unit 800 according to an exampleembodiment. The filter unit 800 shown in FIG. 13 is the same as thefilter unit 600 shown in FIG. 11 except that a pattern reflection layer830 is in contact with both of the inner surfaces of first and secondBragg reflection layers 620 and 640.

FIG. 14A is a plan view illustrating a filter unit 900 according to anexample embodiment, and FIG. 14B is a cross-sectional view illustratingthe filter unit 900 shown in FIG. 14A.

Referring to FIGS. 14A and 14B, the filter unit 900 includes a cavitylayer 910, a Bragg reflection layer 920 provided on a surface of thecavity layer 910, and a pattern reflection layer 930 provided on anopposite surface of the cavity layer 910.

For example, when the Bragg reflection layer 920 is provided on a lowersurface of the cavity layer 910, the pattern reflection layer 930 may beprovided on an opposite surface of the cavity layer 910, for example, anupper surface of the cavity layer 910. Here, the pattern reflectionlayer 930 may increase reflectance in a narrow wavelength range bycausing GMR. To this end, the pattern reflection layer 930 includes apattern material layer 940 and a plurality of holes 935 periodicallyformed in the pattern material layer 940.

The pattern material layer 940 may include a semiconductor materialhaving a given refractive index. For example, the pattern material layer940 may include Si (refractive index=about 3.8). However, this is anon-limiting example. For example, the pattern material layer 940 mayinclude a material such as GaAs, GaP, SiN or TiO₂. In addition, thepattern material layer 940 may include various materials depending ondesign conditions such as the wavelength of incident light.

The holes 935 may be arranged on the upper surface of the cavity layer910 in a two-dimensional pattern. Referring to FIGS. 14A and 14B, eachof the holes 935 has a circular cross-sectional shape, and the holes 935are periodically arranged in a tetragonal pattern on the upper surfaceof the cavity layer 910. Here, the holes 935 may be arranged with apitch less than a resonance wavelength corresponding to the filter unit900. In addition, referring to FIGS. 14A and 14B, the holes 935penetrate the pattern material layer 940. However, this is anon-limiting example. For example, the holes 935 may not penetrate thepattern material layer 940.

The cavity layer 910 may be provided between the Bragg reflection layer920 and the pattern reflection layer 930. The cavity layer 910 mayinclude a material having a less refractive index than the patternmaterial layer 940 of the pattern reflection layer 930. For example, thecavity layer 910 may include SiO₂ (refractive index=about 1.46).However, this is merely an example. For example, the cavity layer 910may include various materials depending on design conditions such as thewavelength of incident light.

In this structure of the filter unit 900, light entering the cavitylayer 910 from the outside of the filter unit 900 may travel in thecavity layer 910 between the Bragg reflection layer 920 and the patternreflection layer 930, and thus, light having a given resonancewavelength may be output to the outside through the Bragg reflectionlayer 920.

As described above, since the holes 935 of the pattern reflection layer930 causing GMR are periodically arranged in a two-dimensional pattern,reflectance may increase in a narrow wavelength range, and thusvariations in resonance wavelength caused by variations in the incidentangle of light on the filter unit 900 may be reduced. According toexample embodiments in which structures causing GMR are periodicallyarranged in a one-dimensional pattern, the effect of reducing variationsin resonance wavelength may be obtained only for light havingpolarization in one direction. In the example embodiment, wherestructures causing GMR are arranged in a two-dimensional pattern, theeffect of reducing variations in resonance wavelength may be obtainedfor light having polarization in all directions.

In addition, filter units 900 having different resonance wavelengths maybe more easily implemented by varying the pitch, thickness, or dutycycle of the holes 935 of the pattern reflection layer 930, and thus itmay be possible to simplify manufacturing processes of a light filterand reduce manufacturing costs and time.

FIG. 15 is a cross-sectional view illustrating a filter unit 1000according to another example embodiment. The filter unit 1000 shown inFIG. 15 is the same as the filter unit 900 shown in FIGS. 14A and 14Bexcept that a filling layer 1035 is filled in a plurality of holes of apattern material layer 1040.

Referring to FIG. 15, a pattern reflection layer 1030 includes a patternmaterial layer 1040 and the filling layer 1035 filled in the holesperiodically formed in the pattern material layer 1040. In this example,the filling layer 1035 may have a thickness equal to or less than thethickness of the pattern material layer 1040. The filling layer 1035 mayinclude a material having a refractive index different from therefractive index of the pattern material layer 1040. That is, thefilling layer 1035 may include a material having a refractive indexgreater than or less than the refractive index of the pattern materiallayer 1040.

FIG. 16 is a cross-sectional view illustrating a filter unit 1100according to an example embodiment. The filter unit 1100 shown in FIG.16 is the same as the filter unit 900 shown in FIGS. 14A and 14B exceptthat a cover layer 1135 covers holes of a pattern material layer 1140 ofa pattern reflection layer 1130.

FIG. 17 is a cross-sectional view illustrating a filter unit 1200according to an example embodiment.

Referring to FIG. 17, the filter unit 1200 includes: a cavity layer1210, a first Bragg reflection layer 1220 including first material layer1221 and second material layer 1222 provided on a surface of the cavitylayer 1210, a second Bragg reflection layer 1240 including firstmaterial layer 1241 and second material layer 1242 provided on anopposite surface of the cavity layer 1210, and a pattern reflectionlayer 1230 provided in the cavity layer 1210.

The pattern reflection layer 1230 includes a pattern material layer 1245and a plurality of holes 1235 periodically formed in the patternmaterial layer 1245. The holes 1235 may be filled with the cavity layer1210.

The pattern material layer 1245 may include a semiconductor materialhaving a given refractive index. In addition, the holes 1235 may bearranged in a two-dimensional pattern on an upper surface of the firstBragg reflection layer 1220. In this case, the holes 1235 may havevarious shapes and may be arranged in a two-dimensional pattern. Here,the holes 1235 may be arranged with a pitch less than a resonancewavelength corresponding to the filter unit 1200. In addition, referringto FIG. 17, the holes 1235 may penetrate the pattern material layer1245. However, this is a non-limiting example. For example, the holes1235 may not penetrate the pattern material layer 1245.

Furthermore, in the example embodiment, the pattern reflection layer1230 is provided in the cavity layer 1210 on an inner surface (that is,the upper surface) of the first Bragg reflection layer 1220. However,the pattern reflection layer 1230 may be provided in the cavity layer1210 on an inner surface (that is, a lower surface) of the second Braggreflection layer 1240.

The other structures shown in FIG. 17 are described in the previousexample embodiments, and thus descriptions thereof will not be repeatedhere.

FIG. 18 is a cross-sectional view illustrating a filter unit 1300according to an example embodiment. The filter unit 1300 shown in FIG.18 is the same as the filter unit 1200 shown in FIG. 17 except that afilling layer 1335 is filled in holes of a pattern material layer 1345of a pattern reflection layer 1330.

FIG. 19 is a cross-sectional view illustrating a filter unit 1400according to an example embodiment.

Referring to FIG. 19, the filter unit 1400 includes a cavity layer 1410,a first Bragg reflection layer 1220 provided on a lower surface of thecavity layer 1410, a second Bragg reflection layer 1240 provided on anupper surface of the cavity layer 1410, and a pattern reflection layer1430 including reflection structures 1435 provided in the cavity layer1410. Here, the pattern reflection layer 1430 may be in contact with theupper surface of the first Bragg reflection layer 1220 and the lowersurface of the second Bragg reflection layer 1240.

The other structures shown in FIG. 19 are described in the previousexample embodiments, and thus descriptions thereof will not be repeatedhere.

FIG. 20A is a plan view illustrating a filter unit 1500 according to anexample embodiment, and FIG. 20B is a cross-sectional view illustratingthe filter unit 1500 shown in FIG. 20A.

Referring to FIGS. 20A and 20B, the filter unit 1500 includes a cavitylayer 1510, a Bragg reflection layer 1520 including first material layer1521 and second material layer 1522 provided on a lower surface of thecavity layer 1510, and a pattern reflection layer 1530 provided on anupper surface of the cavity layer 1510.

A plurality of reflection structures 1535 may be arranged on the uppersurface of the cavity layer 1510 in a two-dimensional pattern. Referringto FIGS. 20A and 20B, each of the reflection structures 1535 has acircular flat surface, and the reflection structures 1535 areperiodically arranged in a tetragonal pattern on the upper surface ofthe cavity layer 1510. Here, the reflection structures 1535 may bearranged with a pitch less than a resonance wavelength corresponding tothe filter unit 1500. The cavity layer 1510 may be provided between theBragg reflection layer 1520 and the pattern reflection layer 1530. Thecavity layer 1510 may include a material having a refractive index lessthan the refractive index of the reflection structures 1535.

As described above, since the reflection structures 1535 of the patternreflection layer 1530 causing GMR are periodically arranged in atwo-dimensional pattern, reflectance may increase in a narrow wavelengthrange, and thus variations in resonance wavelength caused by variationsin the incident angle of light on the filter unit 1500 may be reduced.In addition, since the reflection structures 1535 causing GMR arearranged in a two-dimensional pattern, variations in resonancewavelength may be reduced for light having polarization in alldirections.

The other structures shown in FIGS. 20A and 20B are described in theprevious example embodiments, and thus descriptions thereof will not berepeated here.

FIG. 21A is a plan view illustrating a filter unit 1600 according to anexample embodiment, and FIG. 21B is a cross-sectional view illustratingthe filter unit 1600 shown in FIG. 21A. Referring to FIGS. 21A and 21B,the filter unit 1600 includes a cavity layer 1610, a Bragg reflectionlayer 1620 including first second material layer 1621 and secondmaterial layer 1622 on a lower surface of the cavity layer 1610, and apattern reflection layer 1630 provided on an upper surface of the cavitylayer 1610. The filter unit 1600 shown in FIGS. 21A and 21B is the sameas the filter unit 1500 shown in FIGS. 20A and 20B except thatreflection structures 1635 of the pattern reflection layer 1630 arearranged in a two-dimensional hexagonal pattern.

FIG. 22A is a plan view illustrating a filter unit 1700 according to anexample embodiment, and FIG. 22B is a cross-sectional view illustratingthe filter unit 1700 shown in FIG. 20A. The filter unit 1700 shown inFIGS. 22A and 22B is the same as the filter unit 900 shown in FIGS. 14Aand 14B except that holes 1735 formed in a pattern material layer 1745of a pattern reflection layer 1730 are arranged in a two-dimensionalhexagonal pattern.

FIG. 23A is a plan view illustrating a filter unit 1800 according to anexample embodiment, and FIG. 23B is a cross-sectional view illustratingthe filter unit 1800 shown in FIG. 23A. The filter unit 180 shown inFIGS. 23A and 23B is the same as the filter unit 1600 shown in FIGS. 21Aand 21B except that each of reflection structures 1835 of a patternreflection layer 1830 has a tetragonal flat surface.

FIG. 24A is a plan view illustrating a filter unit 1900 according to anexample embodiment, and FIG. 24B is a cross-sectional view illustratingthe filter unit 1900 shown in FIG. 20A. The filter unit 1900 shown inFIGS. 24A and 24B is the same as the filter unit 1700 shown in FIGS. 22Aand 22B except that each of holes 1935 formed in a pattern materiallayer 1945 has a tetragonal cross-sectional shape.

FIG. 25A is a plan view illustrating a filter unit 2000 according to anexample embodiment, and FIG. 25B is a cross-sectional view illustratingthe filter unit 2000 shown in FIG. 25A. The filter unit 2000 shown inFIGS. 25A and 25B is the same as the filter unit 2000 shown in FIGS. 20Aand 20B except that each of reflection structures 2035 of a patternreflection layer 2030 has a tetragonal cross-sectional surface.

FIG. 26A is a plan view illustrating a filter unit 2100 according to anexample embodiment, and FIG. 26B is a cross-sectional view illustratingthe filter unit 2100 shown in FIG. 26A. The filter unit 2100 shown inFIGS. 26A and 26B is the same as the filter unit 900 shown in FIGS. 14Aand 14B except that each of holes 2135 formed in a pattern materiallayer 2130 has a tetragonal cross-sectional shape.

According to the example embodiments, a pattern reflection layerincluding periodic structures causing GMR is provided to a filter unit,thereby increasing reflectance in a narrow wavelength range and reducingvariations in resonance wavelength caused by variations in the incidentangle of light. In addition, filter units having different resonancewavelengths may be implemented by varying the pitch, thickness, or dutycycle of reflection structures of pattern reflection layers, and thus itmay be possible to simplify manufacturing processes of a light filterand reduce manufacturing costs and time.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exampleembodiment should typically be considered as available for other similarfeatures or aspects in other example embodiments.

While example embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. A light filter comprising: a plurality of filterunits having different resonance wavelengths, wherein each of theplurality of filter units comprises: a cavity layer configured to outputlight of constructive interference; a Bragg reflection layer provided ona first surface of the cavity layer; and a pattern reflection layerprovided on a second surface of the cavity layer opposite to the firstsurface and configured to cause guided mode resonance of light incidenton the pattern reflection layer, the pattern reflection layer comprisinga plurality of reflection structures that are periodically arranged,wherein the pattern reflection layer further comprises a filling layerfilled in gaps between the plurality of reflection structures, thefilling layer being in contact with side surfaces of each of theplurality of reflection structures, and wherein a refractive index ofthe filling layer is different from a refractive index of the pluralityof reflection structures.
 2. The light filter of claim 1, wherein theplurality of reflection structures are periodically arranged with apitch less than a resonance wavelength of each of the plurality offilter units.
 3. The light filter of claim 1, wherein a resonancewavelength of each of the plurality of filter units is determined by atleast one of a pitch, a thickness, and a duty cycle of the plurality ofreflection structures, the duty cycle of the plurality of reflectionstructures being a ratio between a width of each of the plurality ofreflection structures and the pitch of each of the plurality ofreflection structures.
 4. The light filter of claim 1, wherein theplurality of reflection structures are arranged one-dimensionally. 5.The light filter of claim 4, wherein the plurality of reflectionstructures are arranged in parallel lines.
 6. The light filter of claim1, wherein the plurality of reflection structures are arrangedtwo-dimensionally.
 7. The light filter of claim 6, wherein the pluralityof reflection structures are repeatedly arranged in a polygonal pattern.8. The light filter of claim 1, wherein the Bragg reflection layercomprises a plurality of material layers respectively having differentrefractive indexes that are alternately stacked.
 9. The light filter ofclaim 1, wherein the pattern reflection layer further comprises aplurality of connection layers configured to connect adjacent reflectionstructures, and wherein a thickness of each of the plurality ofconnection layers is less than a thickness of the plurality ofreflection structures.
 10. A spectrometer comprising: a light filtercomprising a plurality of filter units, the plurality of filter unitshaving different resonance wavelengths; and a sensor configured toreceive light that has passed through the light filter, wherein each ofthe plurality of filter units comprises: a cavity layer configured tooutput light of constructive interference; a first Bragg reflectionlayer provided on a first surface of the cavity layer; and a patternreflection layer comprising a plurality of reflection structures thatare provided on a second surface of the cavity layer opposite to thefirst surface or included in the cavity layer, the pattern reflectionlayer being configured to cause guided mode resonance of light incidenton the pattern reflection layer, wherein the plurality of reflectionstructures are provided on the second surface of the cavity layer,wherein the pattern reflection layer further comprises a filling layerfilled in gaps between the plurality of reflection structures, thefilling layer being in contact with side surfaces of each of theplurality of reflection structures, and wherein a refractive index ofthe filling layer is different from a refractive index of the pluralityof reflection structures.
 11. The spectrometer of claim 10, wherein theplurality of reflection structures are periodically arranged with apitch less than a resonance wavelength of each of the plurality offilter units.
 12. The spectrometer of claim 10, wherein a resonancewavelength of each of the plurality of filter units is determined by atleast one of a pitch, a thickness, and a duty cycle of the plurality ofreflection structures, the duty cycle of the plurality of reflectionstructures being a ratio between a width of each of the plurality ofreflection structures and the pitch of each of the plurality ofreflection structures.
 13. The spectrometer of claim 10, wherein theplurality of reflection structures are arranged one-dimensionally ortwo-dimensionally.
 14. The spectrometer of claim 10, wherein theplurality of reflection structures are provided in the cavity layer, andwherein each of the plurality of filter units further comprises a secondBragg reflection layer provided on the second surface of the cavitylayer.
 15. The spectrometer of claim 14, wherein the plurality ofreflection structures are in contact with the first Bragg reflectionlayer and the second Bragg reflection layer.
 16. The spectrometer ofclaim 10, wherein the sensor comprises an image sensor or a photodiode.